Integrated circuit technology relies on transistors to formulate vast arrays of functional circuits. The complexity of these circuits require the use of an ever increasing number of linked transistors. As the number of transistors required increases, the surface space on silicon chip/die dwindles. It is one objective, then, to construct transistors which occupy less surface area on the silicon chip/die.
Metal-oxide semiconductor field effect transistors (MOS transistors) are prevalent in integrated circuit technology because they generally demand less power than their counterpart, bipolar transistors. Bipolar transistors, on the other hand, also possess certain advantages over MOS transistors, such as speed. Therefore, it is another objective and attempts have been made to combine the technological designs of bipolars and MOS transistors in an effort to maximize the benefits of both transistor types.
Various types of lateral transistors have been historically described and utilized in complementary metal-oxide semiconductor (CMOS) technology. Lateral bipolar transistors have received renewed interest with the advent of bipolar complementary metal-oxide semiconductor (BiCMOS) technologies. Recently the action of newer devices has been described in new terms and a more careful distinction made between the different types of transistor action possible. Both gate-body connected MOS transistors and gated lateral bipolar transistors have been described. The term gate-body connected transistors is used to describe vertical or other device structures where the body of the MOS transistor also serves as the base of a bipolar transistor but each device functions separately as a normal transistor and MOS transistor action is dominant. Applying the gate voltage to the body serves primarily to change the threshold voltage of the MOS transistor.
Other structures are possible where the gate and base are common and the bipolar transistor and MOS transistor are in parallel but the bipolar transistor current is dominant. In a gated lateral transistor, not only the structures but also the operation is merged and most current flows along a surface under the gate in either MOS or bipolar operation. In the case of a gated lateral bipolar transistor, at low gate voltages around threshold (V.sub.t), they can act as gate-body connected MOS transistors. At higher input voltages, V.sub.t or more, the bipolar action can dominate and they are more appropriately described as gated lateral bipolar transistors.
Much effort has been placed into the study of these merged transistor structures. Both vertical and lateral structures have been studied . These studies do not look to solutions for conserving precious die space in the fabrication of integrated circuits. Likewise, previous efforts have not been able to combine low power operation with enhanced operation characteristics and simultaneously maximize switching speeds. It is desirable then to improved transistor structures, circuits and methods which have advanced operation characteristics and low power consumption. Any improved configuration of transistor structure should remain fully integrateable with prevalent integrated circuit design.